Feeling blue without a reason? Hypothyroidism can be the reason behind your occasional mood swings and anxiety. On the other hand, a hyperactive thyroid can be making you irritable, angry, and upset. Depression that doesn’t improve with antidepressants can be primarily because of thyroid disease. Patients suffering from thyroid problem do not always realize how cranky they have become, but their partners generally report it. What actually happens is that the body gets fired up due to overproduction of thyroid, and this causes agitation.